The present invention is related to gas turbine engines, and more particularly to the cooling of electronics in the environment of gas turbine engines.
Gas turbine engines operate by combusting fuel in compressed air to create heated gases with increased pressure and density. The heated gases are ultimately forced through an exhaust nozzle, which is used to step up the velocity of the exiting gases and in turn produce thrust for driving an aircraft. In modern aircraft, the rate at which fuel is supplied to the engine is typically controlled electronically via an Electronic Engine Control (EEC) device. EECs with autonomous control over engine fuel regulation, and no capacity for pilot override, are commonly called Full Authority Digital Engine Control (FADEC) units. An EEC (or FADEC) receives input of multiple variables, including engine pressure and temperature, throttle state, and fuel pressure, and must therefore be connected to the engine and fuel systems. The engine environment, however, can reach extreme temperatures during operation. High temperatures diminish the lifetime of the electronics of the EEC, and in extreme temperatures the EEC may cease to function altogether.
Military and commercial aircraft typically utilize different methods for keeping the EEC cool. In military aircraft, the EEC is frequently mounted on the engine duct, a hot location, and cooled with relatively cool fuel. This fuel either runs directly through the EEC, or through a cooling plate adjacent to the EEC. In commercial engines, by contrast, the EEC is usually mounted on the fan case on the front of the engine housing, a cooler area away from the heat of the engine, so that the EEC does not require fluid cooling.
There are distinct disadvantages to both existing methods for keeping the EEC cool. The distance of the EEC from the engine in a commercial system necessitates a long, heavy harness for wiring and support, to connect the EEC to the engine and fuel system. If cooling were not an issue, the EEC could be placed close to the engine to minimize complexity and reduce weight by as much as 45 kg (˜100 lbs) or more.
Typical configurations in military aircraft already place the EEC close to the engine, but existing cooling methods are no longer adequate to reliably keep the EEC cool. Engines and fuel have become hotter as engine loads have increased over the last 20 years, shortening EEC lifetimes and making EEC temperature a limiting factor in aircraft operations.